Liquid metal nanoparticles as photo-initiators for preparation of transparent hydrogel with adjustable mechanical properties

To achieve rapid preparation of hydrogels without using conventional chemical initiators, a stable suspension of eutectic gallium indium (EGaIn) liquid metal nanoparticles is explored by probe-sonicating the metal in an aqueous solution. Liquid metal suspension was sonicated to serve as a photo-initiator for acrylamide polymerization and produce hydrogels. The initiation effect comes from the fact that liquid metal suspension after sonication can produce a large number of free radicals when exposed to ultraviolet (UV) radiation, leading to initiation. The changes of liquid metal nanodroplets under UV light irradiation have been systematically investigated. Further, the liquid metal colloidal solutions were used to prepare hydrogels with the same transparency and adjustable mechanical properties as the samples initiated by commercial photo-initiators. This work shows the great application potential of liquid metal in the preparation of hydrogels and provides a new technical idea for the design of multifunctional hydrogels.